Revert "[build] Debug means debug!"

This reverts commit 984c407bb303304ab48ac39a2e4f91d0e987884a.

Reason for revert:
This change causes failures on the flutter engine tests.
Reverting for now to unblock the Dart roll.

https://github.com/dart-lang/sdk/issues/34872


Original change's description:
> [build] Debug means debug!
> 
> Bug: https://github.com/dart-lang/sdk/issues/29458
> Change-Id: Ic7d4cb81c65da9c7a8970431b4e02f3d2d19e556
> Reviewed-on: https://dart-review.googlesource.com/c/77980
> Reviewed-by: Siva Annamalai <asiva@google.com>
> Reviewed-by: Zach Anderson <zra@google.com>
> Commit-Queue: Ryan Macnak <rmacnak@google.com>

TBR=rmacnak@google.com,zra@google.com,asiva@google.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: https://github.com/dart-lang/sdk/issues/29458
Change-Id: I45ea9e1408d71e79d28d8ff0f5aea7649d5fb2ac
Reviewed-on: https://dart-review.googlesource.com/c/80920
Reviewed-by: Aart Bik <ajcbik@google.com>
Commit-Queue: Aart Bik <ajcbik@google.com>
diff --git a/runtime/runtime_args.gni b/runtime/runtime_args.gni
index 9009ed4..16fff64 100644
--- a/runtime/runtime_args.gni
+++ b/runtime/runtime_args.gni
@@ -6,7 +6,7 @@
   # Instead of using is_debug, we introduce a different flag for specifying a
   # Debug build of Dart so that clients can still use a Release build of Dart
   # while themselves doing a Debug build.
-  dart_debug = is_debug
+  dart_debug = false
 
   # Set the runtime mode. This affects how the runtime is built and what
   # features it has. Valid values are: